Automatic control system for furnaces



Aug. 20, 1940. o. D. RICE 4 AUTOMATIC CONTROL SYSTEM FOR FURNACES FiledJan. 14, 1938 3 Sheets-Sheet l I a L NNN WNN

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v mml MW NNN O. D. RIC-E AUTOMATIC CONTROL SYSTEM FOR FURNACES 3Sheets-Sheet 2 Filed Jan. 14, 1938 4 gfR/ce 4 A w 9 gmww Au 20, 1940. 0,11 mm:

AUTOMATIC CONTROL SYSTEM FOR FURNACE-S Filed Jan. 14, 193 8 3Sheets-Sheet 3 MM N NMN F\ I I WNN www

mum N NNN INVENTOR Orw'l/e 0. Rice Patented Aug. 20, 1940 2,211,988AUTOMATIC CONTROL SYSTEM Fort FURNA Orville D. Rice, Mount to The RustFurnace Company,

CES

Lebanon, Pa., assignor Pittsburgh,

Pa., a corporation of Delaware Application January 14, 1938, Serial No.184,980 '1 Claims. (01. 236-) This invention relates to regenerativesoaking pit furnaces. More particularly it relates to a control systemfor automatically operating the.

tofore have usually been arranged in a battery I and provided with meansfor reversing the direction of firing of all holes or pits in thebattery simultaneously. Such arrangement is objectionable since it doesnot permit any flexibility in the control of the several holes andprecludes the use of automatic control since conditions may vary amongthe several holes of a battery so that an adjustment (of fuel or airsupply or the like) which would be appropriate for one hole might leadto a serious disturbance of the conditions in another.

I have invented a novel arrangement of soaking pits, together with anautomatic control system therefor which overcomes the aforementionedobjections. In accordance with my invention, each hole of a battery iscontrolled, and the direction of firing therethrough reversed, entirely30 independently of the other holes in the battery.

The automatic control system includes means for regulating thesupply offuel and air in accordance with the pit temperature to maintain thelatter substantially constant, as well as means responsive to thepressure of the combustion gases in the pit for controlling the stackdampers. The latter are also automatically controlled to effect reversalof the direction of firing at predetermined intervals;

Further details and advantages of the invention will become apparent asthe following detailed description proceeds. This description is to beread in connection with the accompanying drawings illustrating a presentpreferred embodiment with a modification. In the drawings: I

Figures 1A, 1B and 1C constitute a diagrammatic layout of a battery ofsoaking pits having the invention associated therewith;

Figure 2 is a circuit diagram illustrating connections between thevarious electric elements shown in Figures 1A and 1B;

Figure 3 is a partial diagrammatic layout illustrating a modification;a.

Figure 4 is a transverse sectional view of an electro-magnetic valve,several of which are employed in the system of'my invention; and

Figure 5 is a diagram showing the manner in which Figures 1A, 1B and 1Cshould be positioned to be read as a single figure. '60 Referring now indetail to the drawings, and

for the present to Figures 1A, 1B and 1C, soaking pits III, II and [2arranged in any convenient manner are each provided with regenerators l3at opposite ends thereof. These may be of known construction and servein' the usual manner to absorb heat from waste gases discharged-from thefurnace pits and subsequently, on reversal of the direction of firing,for preheating the air supplied thereto for combustion. Passages l4 andi5 extend from the regenerators associated with the pit ill to a stackflue I6, The flue is connected with a stack (not shown). The flow ofwaste gases from the furnace through the passages II and I5 iscontrolled in a manner to be explained more fully hereafter by dampersl1 and I8. Passages l9 and are connected .to the regenerators of the pitH and passages 21 and 22 to the regenerators of pit l2, serving the samepurpose as the passages l4 and I5.

The following description will be confined to .the control mechanism andoperation of the pit Ill but it will be understood that similar controlequipment is provided for the pits II. and I2 whereby the latter operatein the same manner as the pit l0, although each pit operatesindependently of all the others.

General arrangement Air for combustion is delivered alternatively toeither of the regenerators at the opposite ends of the pit ill by ablower 23 driven by a motor 24. The blower 23 supplies air to a mainduct 25 having branch ducts 26 and 21 connected thereto. The ducts 26and 21 communicate respectively with the passages I4 and l5. The volumeof air passing through the main duct 25 is controlled by a valve 23. Thevalve 23 is operated by a double acting fluid-pressure cylinder andpiston 29 controlled by a regulator 30 in a manner to be described morefully later.

The flow of air through the ducts 26 and 21 is controlled by valves 3|and 32. The valves 3| and 32 are provided with self'closing springs andpneumatic actuators 33 of the diaphragm type effective to open thevalves on the admission of air under pressure thereto. Compressed airfor supplying the actuators 33 is maintained in a storage tank T.Electro-magnetic valves 34 and 35 are connected in a piping systemindicated generally at 36 for controlling the operation of the actuators33. These valves are 3-way valves.

When their solenoids are energized, the valves connectthe actuators tothe compressedair supply. When the solenoids are (la-energized, thevalves cut off the air and vent the actuators to atmosphere.

I provide mean types of fuel to the furnace Ill andmeans forautomatically controlling the supply of either. A blast-furnace gas main31 has branches 38 and for supplying two different 39 leading to headers40 associated with the regenerators 13 of the pit ID. A coke-oven gasmain 4| has branches 42 and 43 leading to headers 44 communicating withinlet chambers 44a on opposite sides of the pit Ill.

A shut-oil. valve 45 is disposed in the main 3! and a similar valve 46in the main 4|.. These valves permit either source of fuel to be used atwill. These valves have fluid-pressure cylinders and pistons 41 and 48similar to that shown in 49. One or the other of the valves 45 and 46 isalways held closed. The position of the other valve is controlled by aregulator 49 to maintain the proper pressure on the fuel supplied to thefurnace. Connections 49a extend from the regulator 49 to the mains 31and 4|.

The branches 38 and 39 extending from the main 31 are provided withvalves 58 and 5| having pneumatic actuators 52 similar to those shown at33. These actuators are controlled by electro-magnetic valves 53 and 54similar to those shown at 34 and 35. Valves 55 and 56 are connected inthe branches 42 and 43 and are operatedby actuators 51. The latter arecontrolled by valves 53 and 54 simultaneously with the actuators 52.

Regulating valves 58 and 59 in the mains 31 and 4| are actuatedsimultaneously by a motor controller 60. The latter is actuated inaccordance with the indication of a recording pyrometer 6| having athermo-couple in the pit ID, by means already known which require nodetailed description. The operation of the pyrometer 6| and thecontroller 60 is such that the supply of fuel is regulated in accordancewith the furnace temperature to maintain the latter substantiallyconstant.

The dampers l1 and I8 serve both as reversing valves to control thedirection of firing of the pit Ill and as regulating valves to maintaina pre-determined pressure of the combustion gases within the pit. Doubleacting fluid pressure cylinders and pistons 62 are provided foroperating the dampers l1 and I8. Counterweights 63 are provided tofacilitate-the operation of the dampers. The operation of the damper I1is controlled by electro-magnetic valves 64 and, 65. Similarly, thedamper 8 is controlled by valves 66 and 61. These valves are identicaland the structure thereof is shown more clearly in Figure 4. Each valvecomprises a casing 68, having ports 69, 10 and II. A valve stem 12 isreciprocable in the casing 68 and has valve disks l3 and 14 adapted tocooperate with seats 15 and 16 respectively. The .stem llis connectedtoan armature cooperating with a solenoid 18. When the solenoid isde-energized the armature falls to the position illustrated in 54,

whereu on the valve disk 13 en a es its seat and p g g the elementsalready described are illustrated in 60 the valve disk I4 moves awayfrom its seat. Ports 59 and 1| are thus connected when the solenoid isde-energized. When the solenoid is energized, the armature 11 and valvestem 12 are raised. The valve disk 13 then moves away from its seat andthe valve disk 14 engages its seat. The ports 10 and H are thusconnected. p v The operijcilon of the dampers l1 and I8 is further contlied by electro-magnetlc valves 18 and simi ar to that which has justbeen describedr Fluid under pressure for operating the pistons in thecylinders 62 is delivered by a pump 8|, to" the outlet of which isconnected a high pressure pipe line 62. The pump is driven by a motor 83and draws fluid from a reservoir 84 to which is connected a low pressureor return pipe line 85.

' It will be understood that the dampers l1 and I8 are alternatelyopened and closed when it is desired to reverse the direction of firingin the pit Ill. The means for doing this automatically will be describedhereafter. The damper which is open is adjusted automatically by meansof a regulator 86 to maintain the desired pressure of combustion gasesin the pit ID. This regul lator is of the diaphragm type. One side ofthe diaphragm thereof is connected to a pressure impulse pipe line 81terminating in a nipple 88 extending into the pit ID. The other side ofthe diaphragm is connected to a compensating 1 pipe line 89 terminatingin a recess 90 in the wall of the pit In. The regulator 86 is thusactuated by the velocity pressure of the combustion gases flowingthrough the pit It. In accordance with this pressure the regulatorcontrols the admis- I sion' of fluid under pressure from a branch 9|connected to the pipe line 82, to port 10 of the valve 19, and thereturn of the low pressure fluid from valve 80 to a branch 92 extendingfrom the low pressure pipe line 85. These operations and 2 theconnections between the regulator and valves will be more fullydescribed below.

In a similar manner, the regulator 30 controls the valve 28 to changethe volume of air supplied in accordance with the changes in the 8amount of fuel delivered. The regulator 30 thus controls the fuel-airratio. It includes a pair of diaphragrns and connections 93 and 94 toopposite sides of orifice plates 95 in the air and gasmains. Theregulator 30 operates the cyl- 3 inder and piston 29 to shift the valve28 sufficiently to maintain a constant ratio between the vvolume of fueland the volume of air delivered to the furnace for combustion.Connections 96 I extend from the cylinder 29 to the regulator 36 whichis also connected to the branches 9! and 92 from the high pressure andlow pressure lines 82 and 85.

The pressure regulator 49 similarly controls the valves 45 and 46. Threeway cocks 91 are 41 provided whereby the regulator 49 may be maderesponsive either to the pressure in the main 31 or that in the main 40and to control either the valve 45 or the valve 46; Additional cocks 98determine whether the valves 55 and 5| or the 5 Valves 55 and 56 areoperated by electro-magnetic valves 53 and 54. To change from one fuelto another, therefore, it is only necessary to change the setting of thecooks 91 and 98. This may be accomplished manually with the appa- 5:ratus shown, or by remote control if electio-magnetic valves areemployed instead of manually operated cocks.

The electrical connections between certain of Figure 2, together withthe additional devices necessary to make the operation of the systementirely automatic. The various electro-magnetic valves 34, 35, 53, 54,64 through 61, 18 and 80 are shown in Figure 2 in the electricalcircuits e5 wherebythey are controlled and are designated by the samenumerals as in Figures 1A and 1B.

vices adapted to be energizedtherefrom, include relays I02 and I03 and alimit switch I04. The operating coil of the relay I02 is connectedacross the motor 24 driving the blower 23. The operatingcoil of therelay I03 is similarly connected across the motor 03 driving the pump8I. The limit switch I04 is controlled by the cover of the pit I (no-tshown) and is opened as soon as the cover is moved from its closedposition. By means of these devices the entire automatic control systemis rendered ineffective in any emer-v manual switch I05 is provided forby-passing the cover limit switch I04 in case it is desired undercertain conditions to continue operation under automatic control afterthe cover has been moved off the pit.

Description of operation-Starting -Normal conditions With the contactsof the various protective devices in the closed position, as illustratedin Figure 2, the system may be placed in operation under automaticcontrol by closing the push button switch I06. This switch has a closingpush button 106a and an opening push button I06b as shown. As soon asthe switch I08 is closed a signal lamp I0! is energized to show that theautomatic control system is functioning.

' The closing of the push button I06 also energizes a contact-actuatingmechanism I08, providing a selector switch I09 is in engagement with itsleft hand contact. The mechanism I08 may be of any desired constructionand operates contacts H0 and III. One or the other of the two sets ofcontacts is always closed and the relative positions of the contacts arereversed periodically by the mechanism I08. In simplest form thismechanism might be a constant speed motor driving a.

. cam shaft effective to operate the contacts perioperatin odically, ina predetermined order which will be explained below.- It is desirable,furthermore, that means be provided for adjusting the time intervalbetween reversals of the contacts. The specific mechanism forcontrolling the contacts I I0 and I I I, however, need not be describedin detail since such devices are well known.

Additional groups of contacts H2 and H3 are operated in accordance withthe position of the switch I09, e. g., by being mounted on a commonshaft. When the switch I09 is in the illustrated position, the contactsH2 are closed and the contacts II3 are opened. The contacts H0 and IIImay be described as reversing contacts because when their relativepositions are changed the direction of firing of the pit I0 is reversed.With these reversing contactsin the positions illustrated in Figure 2,electro-magnetic valves 35, 34 and 65 are energized, the circuitstherefor extending from the left hand contact of switch I09 ,(which isconnected to the left hand conductor of the supply circuit IOI by thevarious protective devices and the push button switch I06) by way of theupper contact III, the sec-' pit l0.

through the various protective devices and .the push button switch I06.r

The solenoids of the electro-magnetic valve 54 and the master relay I00are also energized by reason of the fact that limit switches I I5 and II6 connected in series therewith are closed for reasons which will beapparentlater. The circuit for energizing the valve 54 and the relay I00is similar to that just traced and includes lower contact I I I, thefirst contact from the left in the group I I2, limit switches I I5 and'I I6, the solenoid of valve 54 and the relay I00 in parallel, thence bythe return conductor I4 to the supply circuit. Indicating lamps I I1 andH8 are also energized as will be readily apparent as they are connectedin parallel with the solenoids of valves 35 and 54 respectively. Theenergizationof relay I00 completes an obvious energizing circuit for thesolenoids of electro-magnetic valves 19 and 80. The circuit extends fromthe left hand conductor of the supply circuit by a branch II9 throughthe contacts of the relay l00 to the solenoids of the valves I9 and 80and thence by the return c'onvalves as above described causes oppositeends of the cylinder 62 to be connected to the conduits I22 and I23.With thisaccomplished, the damper I1 is actuated by the piston in thecylinder 62 in accordance with the pressure in the pit I0. As alreadyexplained, the regulator 86 connect's the conduits I20 and l2I' to thehigh pressure and relief branches 9| and 92 depending upon the pitpressure. In this way fluid under pressure is supplied to and relievedfrom opposite ends of the cylinder 62- to adjust the position of thedamper H in accordance with the pit pres sure. 7

The energization of the solenoid of valve opens'the valve 32 admittingair for combustion in the furnace from the main duct 25 through thebranch duct 21' to the passage I5; The damper I8 having been closed in amanner which will, be explained later, the air for combustion traversesthe generator I3 on its way toward the The energization of thesolenoidof the valve 54 causes the opening of one of the valves El and58 depending on which source of fuel is being utilized. In either casethe fuel is mixed with the vair and the mixture passes into the furnacefor combustion. The resulting pressure of combustionvgases in the pitoperates the regulator 88 in the mannerv described to control the extentto which the damper I! is opened. The valve 28 is controlled by theregulator '30 to proportion the air-flow to the flow of fuel.

A cycle of firing from right to left having thus been started, continuedoperation is controlled by the various regulators. The volume of fueldelivered from the source thereof is controlled by one of the valves 58and 59 through the motor controller 60 which is actuated in accordancewith the temperature in the pit as indicated by the thermo-couple of thepyrometer GI. The regulator 30 controls the supply of air in accordancewith thesupply of fuel to' maintain constant the ratio between thevolumes thereof.

' GI and 65 causes the latter to connect .site ends of the cylinder 62associated with Automatic reversal-First stage Conditions continue asdescribed until the end of the time for which the reversing mechanismI88 is-set. At that time, the contacts III are opened and contacts IIIIare closed in a pred termined order, viz., (1) .lower contact, IIIopened, (2) upper contact III opened and lower contact IIIl closed, and(3) upper contact H8 closed. The opening of the lower contact III de--energizes lamp I8, the solenoid of valve 58 and the relay I". The latterin turn de-energizes the solenoids of valves I8 and 88. Thede-energization of the solenoid of valve 54 causes the closing of one orthe other of valves 8| and 58 depending upon which fuel is beingemployed. This terminates the supply of fuel to the pit.

When the flow of fuelis terminated by the deenergi'zation of thesolenoid of valve 58, the regulator 88 operates to close the valve 28because the regulator always maintains the valve 28 in a position toprovide an air flow proportional to the flow of fuel.

Thede-energization of the solenoids of valves I8 and 88 causes conduitsI22 and I-28 to be con.- nected to the? relief line 85 and the highpressure line 82 respectively, for the purpose of opening valve I8 in amanner which will be described shortly.

The upper contact .I II is next opened, de-energizing the solenoids ofvalves 85, 54 and 85.

The de-energization of the solenoids of valves the oppodamper I! to theconduit I25 and a similar conduit I21 respectively. These conduits areperma- I switch I I6 is perated by damper I1, being opened when thedamper I1 isclosed, and closed as soon as the damper starts to open. Thecircuit in which the switch 8, is connected is already broken, however,at the lower contact" II I. The. closing of the damper also closes alimit switch I28 which will be referred to again later. This switch isclosed when the damper is closed and opened as soon as the damper beginsto open.

As a result of the de-energization of the solenoid of valve 85, thelatter closes and permits valve 82 to beclosed by its self-closingspring to with the opening of the upper contact I I I. The a cut off thesupply of air to thepass'age I5.

.The first part of the reversing operation is now completed since fuel,and air have been cut off from the right hand end of the furnace andthe damper II closed.

AutomaticreversaL-Second stone The lower contact no is closedsimultaneously closing of the lower contact IIO energizes the solenoidsof valves 84, 88 and 81 and energizes In accordance with I 2,211,9sa

the signal lamp I28. The energization of the solenoids of valves 88 and81 connects the right hand end of the cylinder 82 associated with thedamper III with high pressure line 82' through valve 88, which remainsde-energized, and the left hand end of the cylinder to the relief line85 through valve I8. The damper I8 is thus promptly opened. In opening,the-damper I8 opens the limit switch H5 and closes a limit switch I88.These limit switches are associated with the damper I8 and are operatedthereby in the same manner as switch H8 and I28 are operated by damperII.

The energization of the solenoid of valve 8| causes the opening of valve8i to connect branch 28 of the air supply to passage I8.

The limit switch I28 having been closed by the closing of damper I1 andthe limit switch III by the opening of damper II8, a circuit is preparedfor energizing a signal-lamp I8I, the solenoid of valve 58 and the relay88. This circuit is completed when the upper contact I I II is closed.

The energization of the solenoid of valve 58 causes the opening of thevalve 58 or valve 55, depending onthe source of fuel being used. Fuel isthereupon supplied to the pit and regulator 88 causes valve 28 to openwhereby a proportional amount of air is also delivered to the pit. Theenergization of relay 8! causes the solenoids of valves 18 and 88 to beenergised. The resulting operation of these valves connects the controlconduits I28 and I2I to opposite ends of the cylinder 82 associated withdamper I8 whereby the latter, after its initial opening, isautomatically I8 permits combustion products to pass along passage I5 tothestack flue I8. The firing of the furnace continues under automaticcontrol until the end of the next half of a complete operating cycle.During this time, as in the previous half cycle, the supply of fuel iscontrolled by the pyrometer '8I and the motor controller 88. The volumeof air is controlled by the regulator 88 in accordance with the volumeof fuel supplied and the opening of the stack damper is controlled bythe regulator 88 to insure that the pressure of gases in the pit remainsubstantially constant.

Second reversal At the end of the next half cycle of operations,

the sequence of changes previously described is repeated. The contactactuating mechanism I88 causes contacts III and III to operate in thereverse of the order previously described, theuppercontactl Ill beingopened first. This de-energizefs 'the'solenoid of valve 58 and the relay88. The

valve 58 terminates the fuel supply while the relay -99 de-energizes'thesolenoids of valves I8 and 88 disconnecting the control conduits 128 andI from the cylinder 82'. On terminationof the fuel supply, regulator 88closes valve 28,

' 28 to the passage I8; and the opening of damper The lower contact IIIis next opened the upper contactl I I closed. The former cuts off theair supply by de-energizing the solenoid of valve 4 sociated with thedamper l8, to the conduit I which is connected by conduit I24 to thehigh pressure line 82. The right hand end of the cyl-- inder issimilarly connected by the de-energization of the solenoid of valve 61,to the conduit I21 and thence by conduit I26 to therelief line 85. Thedamper I8 is thus closed, opening the limit switch I30 and closing thelimit switch H5.

The closing of the upper contact III energizes the solenoids of valves35, 64 and 65 and lamp Ill.

The energization of the solenoid of valve causes opening of the valve 32in the branch 21. The energization of the solenoids of valves 64 and 65causes the right hand end of the cylinder 62 associated with damper I1to be connected to the high pressure line 82 and the left hand end tothe relief line 85 through valves 19 and 80, the solenoids of whichremain de-energized.

The lower contact III then closes completing the circuit of the solenoidof valve 54, relay I00 and lamp H8. The operation of the valve 54 causesthe opening of one of the fuel valves 5|,

56. The operation of relay I00 causes the energization, of the solenoidsof valves 19 and 80 which connect the cylinder 62 through valves 66 and61 to control conduits I20 and I2I extending to the regulator 86.

The second reversal of a complete cycle is thus effected and the cyclewill be repeated at the desired intervals so long as the switch I06remains closed.

If it is desired to reverse the direction of firing manually, this maybe done by operating switch I09 and contacts H2 and H3 to theiralternate positions. The opening of contacts II2 disconnect the valvesolenoids and relays already described from the reversing contacts H0and III while the closing of contacts H3 connects manual reversingswitches I32 and I33 in circuit to control the valve solenoids and re--lays. The movement of switch I09 to. its right. hand contactde-energizes the contact-actuating mechanism I08 and completes thecircuit from the switches I32 and I 33.

when changing from automatic to manual reversing, the manualreversingswitch corresponding to the direction of firing then in progress shouldbe closed before the switch I09 and contacts H2 and H3 are'operated.When it is desired to eiiect a manual reversal, the reversing switchwhich is closed is opened and the opened switch closed. The contacts ofthe manual reversing switches are constructed to operate sequentially ina manner corresponding to that of contacts H0 and III, and effectreversal of the direction of firing the pit in the same manner as thelatter. a

When it 'is desired to shut down the pit I0, it is only necessary topress the button I06b of switch I06. This immediately de-energizes thesolenoids of the valves controlling. the supply of fuel and air andde-energizes the master relay (99 or I00) which is energized at theinstant, to cause de-energization of the solenoids of the valves 19 and80. In the manner already described, this causes the closing of thedamper valve which happens to be open,,because the solenoids of thevalves associated with the open damper (either 64 and 65 or 66' and 61)are likewise de-energized.

Assuming that, at the instant of shutdown,

' the damper valve I1 is open,'the de-energization of the solenoid ofvalves 19 and causes the valve I1 to close, as described under AutomaticreversalFirst stage, because the solegases in the pit.

in the same manner as in the system of Fig. 2,

noids of valves 64 and 65 are de-energized si-' multaneously with thede-energization of the solenoids of valves 19 and 80, the current supplyto all valve solenoids and master relays 99 and I00 being interrupted bythe opening of switch I06. The damper valve I8, being closed at theinstant of shutdown, remains closed because to open it requiresenergization of the solenoids of valves 66 and 61.

It will be apparent that the opening of the contacts of relay I02 or theopening of limit switch I04 would have the same resultas just described.The by-passing switch I05 permits continuation of pit firing while thecover is moved off sufliciently to permit the flame to be observed. Theopening of the contacts of relay I03 on failure of the current supply ofpump motor 63 would shut off the fuel-and air.

In a modified form of the invention, I dispense with the valves 19 and80, and connect the regulator 86 permanently to conduits I22 and I23.This modification is shown in Fig. 3 wherein conduits I20 and I 2I-'extend from the regulator 86 to the conduits I22 and I23. In this-system, instead of conecting the cylinder 62 directly to the highpressure and relief lines 82 and 85 to effect full stroke operation ofthe dampers I1 and I8, I provide means for artificially loading theregulator 86 at the time of reversal so that such full stroke operationwill result. This means includes a connection I32 from the air supplyduct 25 to the impulse line 81, a solenoid valve .I33 in said connectionand orifice plates I34 in the impulse line 81 and the connection I32.The valve I33 is constructed to close when its solenoid is energized.This solenoid is connected in the circuit shown in Fig. 2 in place ofthe solenoids of valves I9 and 80 and'is energized when either of therelays 99 and I00 closes its contacts.

Except for the features just described, the modified system is the sameas that of Figures 1A, 1B, 1C and 2 but the remainder of the system hasnot been duplicated in the drawings. In explaining the operation of thesystem of Fig. 3, however, the existence of the other elements of thesystem first described will be assumed.

When the elements of Fig. 3 occupy their illustrated positions, the pitI0 willbe fired from right to left since the damper I1 is opened and thedamper I8 closed. The fuel and air-are delivered and controlled in themanner previously explained. The solenoids of valves 64 and 65 areenergized to connect opposite ends of the cylinder 62 associated withdamper I1 to the regulator 86 through conduits I22, I23 and I20 and I2Iwhereby the regulator operates the damper to maintain the desiredpressure of The relay I00 is energized and, in turn, causes the solenoidof valve I33 to be energized. This cuts off the impulse line 81 from theair duct 25.

When the contact actuating mechanism I08 operates the contacts H0 andIII, in the manner previously set forth, the fuel and air are cut offfrom the right hand end of thefurnace and the relay I00 is de-energizedas are also the solenoids of valves 64 and 65. The latter cause thedamper I1 to be closed as previously explained.

De-energization of the solenoid of valve I33 permits the valve to beopened by any suitable means, such as a biasing spring, whereupon thefull pressure developed by the blower 23\is communicated throughconnection I32 to the imin either direction until pulse line 81. The airpressure applied to the impulse line 81, because of the location of theorifice plates I34 artificially loads the regulator 86, causing it tooperate as if excessive pres-" 6 sure existed in the pit. .The normaloperation of the regulator under such condition is to effect opening ofthe damper to which it is connected at the time. Since thede-energization of the solenoids of valves 6| and 65 has cutoff 10 the-cylinder 62 associated with damper I1 from the regulator'86, the latteris efi'ective, as soon as the solenoids of valves 65 and 61are.energized, to cause full. opening of the damper l8. As alreadyexplained, energization of the solenoids of valves 66 and 61 occurs indue course during the reversing operation. Air and fuel are likewisedelivered. to the left hand side of the pit by operation of otherelements of the automatic control system, whereupon firing in thereverse direction (left to right) proceeds immediately. The relay 8!isenergized during the course of the reversing operation and causesenergization of the solenoid of valve I33. As before, this cuts off theimpulse line 81 from the air supply duct 25 and artificially loading ofthe regulator 86 is terminated. Thereafter, the regulator operates thedamper in accordance with the actual gas pressure in the pit.

The numerous advantages'of the invention will be readily apparentfromthe foregoing description. The provision of a completely automaticcontrol system eliminates all manual operations which have heretoforebeen necessary in' reversingregenerator furnaces. The invention alsomakes it possible to control independently each hole of a battery ofsoaking pits. The reversing dampers are employed as regulating dampers,thus saving the initial cost of a special draft regulating damper andadapting the system to cerqo tain applications where such additionalregulating damper cannot be employed;

v The fuel supply is controlled automatically to 'maintain the desiredtemperature in.the pit and the airsupply is regulated in proportion tothe volume of fuel supplied. Alternate: fuel supply systems are providedand means whereby one or theother can be brought into action at anytime. The stack draft is regulated to maintain the desired pressure ofgases in the pit.

Numerous safety and interlocking features have been provided. Failure ofthe air supply causes the system-to shut down automatically. The same istrue of movement of the cover of the'pit from its closed position,except when it is .55 desired to observe the fiame conditions in .the

pit. In case of failure-of the supply of hydraulic pressure utilized tooperate various valves, the

fuel and air are cut o'if automatically. The

damper limit switches prevent initiation of firing proper position. I a

Manual control means'are provided to pe mit automatic reversalto besuspe ded if desired. The various steps performed in reversing op- 5eration are indicated by signal! paso that the condition of all theelements may be determined by a quick observation.

Although I have illustrated and described herein but a preferredembodiment a'ndpne modification of the invention, it will be clear thatchanges in the construction and operation .disclosed may be made withoutdeparting from the spirit of the invention or the scope of the ap-"pended claims.

75 I claim:'

the dampers are in 1. A control system for a regenerative furnace havingreversing dampers, comprising means for periodically closing one damperand opening another, and means responsive to the pressure of the gas inthe furnace for controlling 6 the extent to which the open damper isopened.

2. A control system for a regenerative furnace having reversing dampers,one of, which is normally closed and the other open to an extent such asto maintain a predetermined pressure in 10 the furnace, comprisingmeans'responsive to said pressure for controlling the open damper, andmeans for applying periodically to said pressureresponsive means atemporary, artificial loading effective to cause quick opening of thedamper 15 which is to operate next as a pressure regulating damper,before the normal gas pressure has actually been built up in thefurnace.

3. In a furnace, a combustion chamber, reversing dampers adapted to bealternately opened 2 and closed. to reverse the direction of firingthrough said chamber, and means for regulating the position of the opendamper in response to variations in the pressure of combustion gases insaid chamber. 25

4. A control system for a regenerative furnace having air and fuelsupply means and reversing dampers, comprising means for closing one ofsaid dampers and opening. the other including a reversing controller andmeans for 30 actuating said controller at predetermined intervals, andautomatic control means responsive to the pressure of the gases in thefurnace for regulating the position of the open damper bei tweenoperations of said controller.

5. In a method of operating a regenerative,

' pit furnace having reversing dampers, including thesteps of firing thefurnace inone direction v after closing one damper and opening theother,

reversing the relative positions of the dampers -nected selectively tothe actuating means of whichever damper is open at-a given time. to

Ieifect adjustment thereof, means for reversing the relative positionsot'the dampers, and means effective on reversal of the dampers todisconq, 3nect said regulator from the actuating means of the damperwhich was formerly open and connect it to the other damper-actuatingmeans.

7. A control system for a regenerative furnace having reversing dampersand fuel and air valves, said system including individual actuators foreach damper and valve, an electro-magnetic control device governingeachactuator, means blessing said control devices to cause closing ofthe valves and dampers when said control devices are de-energized." saidcontrol devices being connected 'to a. common supply circuit through amaster controller, a blower supplying 1 air to said furnace, a motorvdriving said blower, 7

and a relay adapted when dc-energized to open said circuit, said relaybeing so connected as to be energized so long as said motor isenergized.

o'avrnm D. RICE.

